feat(analysis): add relative date filters for Analysis Mode (#566)

[cct08311github]

Summary

• Frontend: createValueInput() for date fields now renders a <span> wrapper with a mode <select> (8 relative tokens + "自訂日期") and a hidden .analysis-filter-value input. collectFilters() is unchanged — deep querySelector('.analysis-filter-value') finds the input inside the wrapper.
• Backend: ResolveRelativeDates() in AnalysisQueryEngine expands @today / @thisWeek / @lastWeek / @thisMonth / @lastMonth / @last30Days / @thisQuarter / @ytd tokens into Gte/Lte FilterCondition pairs before ApplyFilters builds expression trees. Unknown tokens throw InvalidOperationException.
• i18n: Both zh-TW and en-US locales updated with reldate.* keys.

Supported Tokens

Token	Expands to
@today	Today 00:00 – 23:59
@thisWeek	Monday – Sunday of current ISO week
@lastWeek	Monday – Sunday of previous ISO week
@thisMonth	1st – last day of current month
@lastMonth	1st – last day of previous month
@last30Days	-30 days to today
@thisQuarter	1st day of current quarter to today
@ytd	Jan 1 of current year to today

Test plan

• 8 MSTest for ResolveRelativeDates (no-op, @today, @last30Days, @ytd, mixed, unknown token throws, @thisWeek Monday, @thisMonth bounds)
• 9 Jest for date mode UI (createValueInput span shape, 9 options, token → hidden input, custom → visible input, collectFilters reads token)
• Updated existing #501 test to match new span-wrapper shape for date fields
• All 529 Jest tests pass; all C# engine tests pass

Closes #566

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